Like alot of us dealing with addicts we learn the art of tough love. I think that you will have to do the same with your grandson. He probably knows exactly what type of person the bf is but what purpose does it really serve in the end? He still is a child and its just gonna end up hurting him. I know you think he should hear the truth but really I think he already knows. And even if you did play it for him it probably would end up backfiring in your face.